Thickened petroleum liquid especially for treating wells



United States Patent THICKENED'PETROLEUM LIQUID ESPECIALLY FOR TREATING WELLS No Drawing. Application April 30, 1957 Serial No. 655,955

Claims. (Cl. 252-855) The invention relates to a liquid composition having a base of petroleum oil, the composition being useful as a vehicle for carrying a particulate solid in suspension into the producing formation of a well as in fracturing wells to stimulate production of oil or gas.

Heretofore in preparing liquids for use in well fracturing operations employing a propping agent in the form of a particulated solid, such as sand, it has been proposed, as in US. Patent 2,667,457, to convert crude petroleum oil, for example, into a fracturing gel by reacting together in the oil about 4 to about weight percent of an aliphatic organic acid having from 16 to 20 carbon atoms and a sufiicient quantity of a base to neutralize the acid. The gels so-prepared are said to possess a sufficiently high viscosity to maintain in suspension the particulate propping material. It is to be inferred from the disclosure of the said patent that the gels are useful for fracturing wells as by the method disclosed in US. Patent 2,596,845; Nevertheless in carrying out these teachings, we have encountered difiiculties which limit their usefulness. One of these is that an inordinarily large amount of these gelling materials is required to obtain thedesired high viscosity and sand carrying ability. Another is the high cost of providing such gels. Still another is the need for a gel breaker to facilitate the removal of the gel from the earth formation after fracturing so that the flow of oil or gas to the well will not behindered by the gel.

Accordingly, it is the principal object of the invention to provide an improved gelled petroleum oil suitable for use in well fracturing operations, for example, without the need for the injection of a gel breaker. Other objects and advantages will appear as the description of the invention proceeds.

The invention is predicated upon the discovery that by reacting, in admixture with petroleum oil, a mixture of tall oil and-at least one of the aliphatic organic acids, octanoic, hexanoic, and decanoicfand an alkali metal hydroxide, the latter being at least in approximately the proportions required to neutralize the acid including that of the tall oil, desirable gellation is obtained quickly with concentrations of tall oil which need not exceed 2 or 3 percent by weight and the amount of the acid added to the tall oil need be but a fraction of the amount of tall oil, for example, from about 10 to percent by weight, about 13.5 percent being preferred. The small quantity of tall oil required when at least one of the aforementioned aliphatic acids is included makes the method economically feasible and no gel breaker need be injected into the earth formation following a fracturing treatment as the gel or thickened oil so-obtained automatically thins on remaining in contact with the crude oil present in oil and gas producing earth formations.

Petroleum oils so-treated have a low filtrate rate and a large capacity to suspend the particulated solids, such as those used in well fracturing operations, particularly sand. To be effective in carrying a particulated solid in suspension, as in well fracturing operations, the falling rate of the solid particles in the vehicle, gelled or thickened in accordance with the invention, should not exceed one foot per minute at F. Oils thickened according to the invention easily meet this requirement.

The following groups of tests are illustrative of the improved properties exhibited by a petroleum oil thickened according to the invention.

In one group of these tests to parts of kerosense having a viscosity of 2 centipoises at 80 F., 1 part of tall oil and mixtures of the tall oil with one of the aforementioned acids were added and in each instance neutralized with an excess of 30 percent aqueous caustic soda solution by stirring the ingredients together. As a result, the kerosene was thickened as shown by viscosity measurements. The pertinent data of these tests are set forth in Table I.

Table I Resulting viscosity at 80 F. after Test 1 part of agent named below added neutralization with No. per 100 parts of kerosene caustic soda solu- I tion in situ in ccntipoises at 8 1 Tall oil alone 43 2 Mixture of 9 partsof tall oil and 1 part 152 of octanoic acid. 3 Mixture of 8.5 parts of tall oil and 1.5 202 parts of octanolc acid. 4 Mixture of 8.0 parts of tall oil and 2.0 200 parts of octanoic acid. 5 Mixture of 8.5 parts of tall oil and 1.5 146 parts of decanoic acid. 6 Mixture of 8.5 parts of tall oil and 1.5 76

parts of hexauoic acid.

1 Tall oil used throughout was Armour Chemical Co. Neofat 4206 having the following composition: rosin acid 6%, oleic acid, 50%, linoleic acid 40%, linoleuic acid and unsaponifiable 4%.

Another advantage resulting from the inclusion of one of the aforementioned acids with the tall oil, on being neutralized in situ in a petroleum oil, is that the gelled oil so-obtained exhibits a greatly lowered fluid loss or filtrate rate as measured by employing the filtration apparatus and process described in American Petroleum Institute, Code 29, second edition, July 1942, Standard Field Procedure for Testing Drilling Fluids (tentative), section V. The group of comparative tests set forth in Table II are illustrative of this using kerosene as the oil being thickened and the amount of the thickening agent being 1 percent of the kerosene weight.

1 After neutralization of the agent in situ with 1.5 percent of NaOH in a 30 percent water solution based on kerosene weight.

The ability of a petroleum oil thickened, in accordance with the invention to suspend sand, is illustrated in the group of tests in Table III. In these tests, kerosene was thickened with various amounts of an acid mixture of 8.5 parts of tall oil and 1.5 parts of octanoic acid and then the rate at which sand (Fliutshot Ottawa sand) of 20 to 40 mesh standard sieve size, descended in a column of the so-thickened oil was measured.

Table 111 Percent 1 Percent 1 of Resulting Sand falling of acid NaOH as 30% viscosity rate, feet Test N0. mixture caustic soda in cps. at per minute added solution [or 80 F. at 80 F.

neutralization 1, i. g y 202 1 less thanQJ 0. 75 1. 2 I 88 Do o. 50 0. 75 54 2 Viscosity and sand carrying capacity, and tofreduce the fluid loss. In Table IV is'a group'of tests illustrative of this using various crude petroleum oils identified as to source. The oils were thickened by. neutralizing in situ, 1.5 percent of NaOH in 30 percent aqueous solution, and 1 percent (based on the weight of the oil) of a mixture of 8.5 parts of tall oil and 1.5-parts of octanoic acid.

as much as three times that required for neutralization. Thealkali is best used-in aqueous solution asin a concentration of to 50 percent. Various amounts of particulate material may be suspended in the oil thickened according to the invention, thereby providing a desirable Well fracturing fluid. Optimum amounts of particulate material are from 1.5 to 3 pounds per gallon of the gelled oil, although other amounts may be used, e.g. from 0.5 to 6 pounds per gallon. It is to be understood that other aliphatic straight chain carboxylicv acids may be used having chain lengths in the range of 6 to 10 carbon atoms.

Weclaimr I 1. The method of increasing the viscosity of'a petroleum liquid which comprises reacting together in admixture with the petroleum liquid, 9.. mixture of' acids, said mixture consisting 10f tall oil anda straight chain aliphatic organic acid having .from sixto, ten carbon atoms in the chain, and a sufli'cient'quantity of an alkali metal hydroxide to at least approximately neutralize the acids of the said mixture, the amount of: the aliphatic organic acid being from 10'to 25 percent of: that of the tall oil by Weight and the. amount of the, mixture ofacids being from 0.75 to 3 percent of the. weight: of'the petroleum liquid.

2. The method according to claim in which the-aliphatic acid is hexanoic'.

Table IV Viscosity, Viscosity, v

Brook- Sand- Brook- A.P.I. field No. 2 falling Fluid 1oss, field N o. 2 Sandfalling Fluid'loss, Formation Oil Gravity Spindle rate 1 API Code 29 Spindle, rate 2 (ft./m1n.) API Oode29 60 F. 60 r.p.m (ft/min.) 60 r.p.m.

' p -l p Hart 66; 8 20 '5. 8 39 ml./30 min 138 less than 0.1..- l 18 m1./30 min. Springer 65. 8 32 5. 7 51 ml./30 mm 142 .do 17 ml.l30 min. Strawn. 47.2 31 4. 4 144 ink/30 min... 35 ink/30 Oil Cree 45. 6 38 6. 9 ./30' N. J. Beagl 39. 8 24 v 2. 7 Gibson 37. 0 32 4. 6

1 Before thickening. 2 After thickening.

In general the neutralization required is eflected by agitating the reagents, that is the tall oil and aliphatic organic acid named and alkali metal hydroxide, in the oil to be thickened preferably at temperature of 60 to 85 F., although other temperatures may be used. Sodium hydroxide is the preferred alkali metal hydroxide, although other alkali metal hydroxides, erg; KOH, may be used. A preferred Way to thicken the oil is to disperse the tall oil and aliphatic organic acid in the petroleum oil first and then disperse the alkali dissolved, in waterin the resulting dispersion. Agitation is preferably continued for 10 to 20 minutes to ensure substantial completion of the neutraliztaion reaction. The amount of alkali used should be at least about that required to neutralize the acids involved as already mentioned. However, the optimum amount to use is approximately 3. The method accordingto claim' 1 in which'the' ali"- phatic acid is decanoic.

4. The method according to claim 1 in-which the ali phatic acid is octanoic.

5. Themethod according to claim 'I-which includes the step of adding to the p etro1eurn liquid -per'gall'on therof fromQS to 6 pounds of particulate .materialsuch 'assand. f

References Cited inithe file-of this patent:

UNITED STATES PATENTS I 2,618,596 Minich et al. I Noilljs; 1 952 2,667,457 McChrystal et a1. Jan. 26,1954 2,687,175 Johnson Aug. 2 4, 195.4 2,794,779 I p, Car-dwell a 211...; June, 4.1952 

1. THE METHOD OF INCREASING THE VICOSITY OF A PETROLEUM LIQUID WHICH COMPRISES REACTING TOGETHER IN ADMIXTURE WITH THE PETROLEUM LIQUID A MIXUTE OF ACIDS, SAID MIXTURE CONSISTING OF TALL OIL AND A STRAIGHT CHAIN ALIPHATIC ORGANIC ACID HAVING FROM SIX TO TEN CARBON ATOMS IN THE CHAIN, AND A SUFFICIENT QUANTITY OF AN ALKALI METAL HYDROXIDE TO AT LEAST APPROXIMATELY NEUTRALIZE THE ACIDS OF THE SAID MIXTURE, THE AMOUNT OF THE ALIPHATIC ORGANIC ACID BEING FROM 10 TO 25 PERCENT OF THAT OF THE TALL OIL BY WEIGHT AND THE AMOUNT OF THE MIXTURE OF ACIDS BEING FROM 0.75 TO 3 PERCENT OF THE WEIGHT OF THE PETROLEUM LIQUID. 